1. Field of the Invention
Embodiments described herein generally relate to a method and apparatus for measuring gas flow. More specifically, embodiments of the invention generally relate to a method and apparatus for measuring gas flows that are provided to a semiconductor processing chamber and related utilities.
2. Description of the Related Art
Accurate control of gas flows is an important process control attribute critical to many microelectronic device fabrication processes. Precise control of process gas flows into the processing chamber is required in order to obtain desired processing results, particularly as critical dimensions and film thicknesses shrink.
Conventional gas delivery systems used with semiconductor processing chambers generally include a mass gas flow meter or mass flow controller (MFC) as the primary flow regulation device. However, the accuracy of MFCs may be affected by a plurality of factors that contribute to an uncertainty of the actual gas flow. For example, the accuracy of the MFC will typically vary with changes in temperature, upstream pressure, and downstream pressure. Deviation from the gas flow set point due to MFC inaccuracy may contribute to processing defects, poor emission control and inefficient waste of costly gases.
Although conventional mass flow control systems have proven relatively reliable, field experience with the existing technology has increased the demand for more accurate measurement of flow. For example, poor control of gas flows used in chemical vapor deposition (CVD) or atomic layer deposition (ALD) applications may result in poor film deposition or etching results, which cannot be tolerated in next generation circuit designs.
Therefore, there is a need for an improved method and apparatus for measuring gas flows so that the delivery of gases in a semiconductor processing system may be performed with greater confidence and accuracy.